(a) Technical Field
The present invention relates to a system method for calculating Distance to Empty (DTE) in an electric vehicle. More particularly, it relates to a method for more accurately calculating DTE by excluding energy consumption used by an air conditioning apparatus from the total energy consumption of a battery
(b) Background Art
Generally, electric vehicles are powered by motors driven via electricity charged in a battery. In electric vehicles, it is very important to know and monitor instantaneous properties of the battery such as the temperature of the battery and the State of Charge (SOC) of the battery. By monitoring these properties, vehicle control systems are able to better maintain the state of the battery at a level that is provides the best efficiency and performance.
A Battery Management System (BMS) is an electronic system that takes into consideration these properties to assist a vehicle in efficient operation. The BMS operates by preventing the shortening of the battery lifespan due to the reduction of the durability of the battery and informing a vehicle controller performing overall control of the SOC information of the state of the battery.
It is particularly important to check the SOC of the battery in electric vehicles that use high voltage batteries, and monitor and report the remaining capacity of the battery to a driver during operation. For example, in internal combustion engine vehicles, a driver is informed of Distance to Empty (DTE) estimated based on the current fuel state. In electric vehicles, however, DTE is estimated from the current battery energy state, and then is shown on a cluster to the driver so that they may estimate how much further they can travel before they need to recharge the vehicle.
Typically, the DTE in an electric vehicle is calculated by estimating the DTE using a relationship between the SOC (%) (the amount of energy remaining in the high voltage battery) and the energy consumption rate per distance.
FIG. 1 is a flowchart illustrating a typical method of calculating DTE. Hereinafter, the typical method of calculating DTE will be described with reference to FIG. 1. More specifically, the DTE in an electric vehicle is calculated by first calculating a past average fuel efficiency (S1), then calculating a current fuel efficiency (S2) and a final fuel efficiency by blending the past average fuel efficiency and the current fuel efficiency (S3), and finally, calculating a DTE from the final fuel efficiency (S4).
Here, the past driving average fuel efficiency is calculated by averaging the fuel efficiency of past driving cycles (i.e., the interval from previous charging to next charging is defined as one driving cycle). The fuel efficiency (km/%) is calculated and stored at the end of every driving cycle (i.e., the previous driving cycle is finished when charging is initiated), and then the stored fuel efficiencies are averaged.
In this case, the fuel efficiency (km/%) of the driving cycle is expressed as accumulation driving distance during a driving cycle (km)/ΔSOC(%), where ΔSOC(%)=SOC(%) immediately after previous charging−SOC(%) just before current charging.
When the final fuel efficiency is calculated, DTE is calculated based on the fuel efficiency, and then displayed on the cluster, etc. In this case, DTE can be expressed as final fuel efficiency (km/%) X current SOC (%). Thus, in calculating DTE of an electric vehicle, the battery SOC is needed. More specifically, when the fuel efficiency of past driving cycles is calculated, the total battery consumption (corresponding to the above ΔSOC) during cycles is reflected.
In electric vehicles, methods for calculating battery SOC are well known. For example, there is a method of calculating the battery SOC by measuring the amount of discharged current per unit hour. These calculated SOC values are being widely used for battery management, DTE calculation, and other purposes for vehicles.
However, often times, the resulting DTE provided to drivers using the above known methods are subject to and result in erroneous values caused from estimation difficulties and incorrect estimation values. Particularly, energy consumption of past driving cycles should be reflected in calculating the DTE, and in this case, the total battery consumption should be reflected. However, since the total battery consumption includes the energy consumed by an air conditioning apparatus during the past driving cycles as well, it is difficult to calculate an exact DTE which excludes this type of energy consumption.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.